Annoying Check engine light

[SMonaldo]

that's where the troubleshooting part comes in, they need to look at ALL of the external possibilities, starting at the battery, grounds, maf, 02 sensors, possible leaks, backpressure test, etc, etc,
if it was a long block they re-used the intake, so smoke test.
all it takes is something being a little too much out of whack and the code is set
it sounds like it happened or happens under a load so that's going to make it a little harder, someone probably needs to do a drive record and look at all the data.
my guess would be something in the intake or exhaust if not a leak on the intake. but the electrical system needs to be ruled out first which is generally easy.

the good news is it is not likely to be the engine

Oh, I'm with you on this. I am an engineer that works in the IT field, and if I went about the process they are following I would have been fired a long time ago. I have always taught people under me to never shotgun an issue, and that's exactly what they are doing. At this point I am strongly requesting they replace the egr, o2, pcv, maf and fuel pressure regulator. After that they can start doing what you suggest while I drive a rental at their cost. Eventually I will have a new engine and all the components @ 70k miles, and a 3 yr 100K mile warranty on GM. I LOVE THE TRUCK.

 

[Doubeleive]

FYI injectors are not part of a long block, so the entire fuel feed system was off the old engine.

ya, I was thinking of a different engine....
but still, warranty coverage should require verification that the part has failed, just doesn't sound like they are digging very deep.
I guess it depends on the warranty, wish I had deep pockets to replace anything suspect lol